Heterocyclic photoconductor containing o, s or se

ABSTRACT

Compounds useful in electrophotography as part of photoconductive elements are disclosed having the general formula:   WHEREIN Z is a sulfur, oxygen or selenium hetero atom and R1 through R4 each represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, an aryloxy group or a halogen atom and Y represents the group -(CH CH)n-R in which n equals 0, 1 or 2 and R is an aryl radical.

United States Patent [191 Virkhaus 1 HETEROCYCLIC PHOTOCONDUCTORCONTAINING O, S OR SE [75] Inventor: Rein Virkhaus, Rochester, N .Y.

[73] Assignee: Eastman Kodak Company,

Rochester, NY.

[22] Filed: Aug. 7, 1972 [21] Appl. No.: 278,303

[52] US. Cl 96/l.5, 96/l.6, 260/239 R,

260/240 D, 260/330.5, 260/346.2 [51] Int. Cl 603g 5/06 [58] Field ofSearch..'. 96/15, 1.6, 1 PC [56] References Cited UNITED STATES PATENTS3,072,479 1/1963 Bethe 96/l.5 3,174,854 3/1965 Stumpf et al. 96/l.53,301,676 l/1967 Tomanek 96/15 [451 Oct. 16, 1973 PrimaryExaminer-Roland E. Martin, Jr. Attorney-Robert W. Hampton et al.

[57] ABSTRACT Compounds useful in electrophotography as part ofphotoconductive elements are disclosed having the general formula:

wherein Z is a sulfur, oxygen or selenium hetero atom and R through Reach represent a hydrogen atom, an alkyl group, an aryl group, an alkoxygroup, an aryloxy group or a halogen atom and Y represents the group-(CH=CH),, R in which n equals 0, l or 2 and R is an aryl radical.

13 Claims, N0 Drawings 7 HETEROCYCLIC PHOTOCONDUCTOR CONTAINING 0, S ORSE This invention relates to electrophotography, and in particular, tophotoconductive compositions and elements.

Electrophotographic imaging processes and techniques are based on thediscovery that certain materials which are normally insulating becomeconductive during exposure to electromagnetic radiation of certainwavelengths after being electrically charged. Such materials, such maybe either organic or inorganic, are termed photoconductors. They areconveniently formed into usable image-forming elements by coating alayer of the photoconductive composition, together with an electricallyinsulating resinous binder where necessary or desirable, onto a suitablesupport. Such an element will accept and retain an electrostatic'chargein the absence of actinic radiation. In use, the surface of the elementis charged in the dark to a uniform potential and exposed to animagewise pattern of actinic radiation, which selectively reduces thesurface potential to produce a charge pattern corresponding to theimagewise radiation pattern. The resultant charge pattern orelectrostatic latent image may be developed by contacting it withsuitably charged marking particles which adhere in accordance with thecharge pattern, or it may be transferred to another insulating surfaceupon which it is developed. The particles may then be fused or fixed tothe surface by known means such as heat or solvent vapor, or they may betransferred to another surface to which they may similarlybe fixed, toproduce a permanent reproduction of the original radiation pattern.

Various photoconductive insulating materials have been employed in themanufacture of electrophoto graphic elements. Nothing as yet has beendiscovered from the large number of different photoconductive substancestested which permits effective prediction, and therefore, selection ofthe particular compounds exhibiting the desired electrophotographicproperties.

It is, therefore, an object of this invention to provide a novel classof photoconductors having useful photosensitivity when electricallycharged.

It is another object to provide novel photoconductorcontainingcompositions which exhibit improved electrical speeds.

These and other objects and advantages of this invention areaccomplished through the use as photoconductors of compoundscorresponding to the general formula:

wherein:

Z is a hetero atom selected from an oxygen atom, a sulfur atom and aselenium atom;

R through R may be the same or different and each represent a hydrogenatom, an alkylgroup, an aryl group, an alkoxy group, an aryloxy group ora halogen atom; and

-CH=OH)Rin which n is Y represents the group wherein:

Z isa hetero atom selected from an oxygen atom and a sulfur atom;

Y represents the group(CH=CH),,-R in which n is an integer from 0 to l;and R is phenyl radical, a methoxyphenyl radical, adi-p-tolylaminophenylradical, a dialkylaminophenyl radical, a diphenylaminophenyl radical ora diphenylaminonaphthyl radical.

The terms alkyl, aryl, etc, as used herein, are intended to have themeanings as hereinafter set forth.

The term alkyl refers to any aliphatic group having one to 18 carbonatoms, e.g., methyl, ethyl, propyl, butyl, isobutyl, octyl, dodecyl,etc, including a substituted alkyl group having one to 18 carbon atomswith such substituents as an alkoxy radical, an aryloxy radical, anamino radical, a hydroxy radical, an aryl radical, an alkylaminoradical, an arylamino radical, a nitro radical, a cyano radical, ahalogen atom, an acyl radical having the formula:

wherein R is hydroxy, hydrogen, aryl, lower alkyl having one to eightcarbon atoms, amino including substituted amino, lower alkoxy having oneto eight carbon atoms, aryloxy, etc.

The term aryl group'refers to an aromatic group, e.g., phenyl, naphthyl,anthryl, fluorenyl, etc. including a substituted aryl group having suchsubstituents as an alkoxy radical, an aryloxy radical, an aminoradical,a hydroxy radical, an alkylamino radical, an arylamino radical, a nitroradical, a cyano radical, a halogen atom, as well as an acyl grouphaving the formula:

wherein R is hydroxy, halogen, hydrogen, aryl, amino, includingsubstituted amino, lower alkoxy having one to eight carbona'toms,aryloxy, lower alkyl having one to eight carbon atoms.

An amino group is a group having the formula:

wherein R and R are the same or different including hydrogen, loweralkyl having one to eight carbon atoms such as ethyl, propyl, butyl,etc, aryl such as phenyl, naphthyl, etc, or halogen, e.g., chlorine,bromine, etc.

An alkoxygroup is a group having from one to about 18 carbon atoms inthe alkyl moiety, e.g., methoxy, propoxy, octoxy, dodecyloxy,octadecyloxy, etc.

An aryloxy group is a group such as phenoxy, naphthoxy, and the like.

Representative photoconductors corresponding to the above formulasincluding the following:

A. 2-benzylidenebenzofb] thiophen-3-one B.2-(p-dimethylaminobenzylidene)benzo[b] thiophen-3-one C.2-(p-diethylaminobenzylidene)benzo [b] thiophen-3-one 1 D.2-(p-diphenylaminobenzylidene)benzo ['b} thiophen-3-one E.Z-(p-dimethylaminocinnamylidene)benzo [b] thiophen-3-one F.Z-(p-methoxybenzylidene)benzo [b] thiophen- 3-one G.2-(p-diphenylamino-o-methoxybenzylidene)- benzo [b] thiophen-3-onel3-dibenzo(a,h )fluorene, 5,10-dioxo-4a, l ldiazabenzo(b )fluorene, 3 l3-dioxo-7-oxadibenzo (b,g)- fluorene, and the like; aggregate typesensitizers of the type described in Light'Belgian Patent 705,1 l 7,dated Apr. 16, 1968; aromatic nitro compounds of the kinds described inU.S. Pat. No. 2,6l0,l; anthrones as disclosed in U.S. Pat. No.2,670,284; quinones U.S. Pat. No. 2,670,286; benzophenones, U.S. Pat.No. 2,670,287; thiazoles, U.S. Pat. No. 2,732,301; mineral acids,carboxylic acids, such as maleic acid, dichloroacetic acid, andsalicyclic acid; sulfonic and phosphoric acids; and various dyes, suchas cyanine (including carbocyanine), merocyanine, diarylmethane,thiazine, azine, oxazine, xanthene, phthalein, acridine, azo,anthraquinone'dyes and the like and mixtures thereof. The sensitizerspreferred for use with the compounds of this invention are selected frompyrylium dye salts,

binder and organic photoconductor to form a sensitizedelectrophotographic element, it is the normal H.2-(p-di-p-tolylaminobenzylidene)benzo [b] thiophen-3-one J.2-(4-diphenylamino-l-naphthylidene)benzo {b} thiophen-3-one While theabove-described compounds are preferred, certain modifications producecompounds which are suitable for use in electrophotography. Exemplary ofsuch modifications would be the compounds having the above formulas (a)wherein the hetero atom is substituted by certain hetero groups such asSO, SO NI-I, NR and NAr wherein R and Ar represent an alkyl and an arylradical, respectively, as described above and (b) wherein the size ofthe heterocyclic ring itself maybe increased from 5 to 6 members. Also,the positions of the hetero atom or group, the =0 and the =CI-I-Y in oron the heterocyclic ring may be'located in an alternative position.Another modification is that the R through R substituents of the benzenering may together complete an optionally substituted heterocyclic orcarbocyclic fused ring system, such as naphthyl, phenanthryl, anthryl,benzonaphthyl, quinolyl, quinazolyl, etc. v

Electrophotographic elements of the invention can be prepared with thephotoconductive compounds of the invention in the usual manner, i.e., byblending a dispersion or solution of a photoconductive compound togetherwith a binder;-when necessary or desirable, and coating or forming aself-supporting layer with'the photoconductor-containing material.Mixtures of the photoconductors'described herein can be employed.Likewise, other photoconductors known in the art such as those describedin Light British Patent 'No. 1,153,506, dated May 29, 1969, can becombined with the present photoconductors.

In addition, supplemental sensitizing materials useful for changing thespectral sensitivity or electrophotosensitivity of the element can beadded to the present photoconductive compositions when it is desirableto produce the characteristic effect of such materials. Sensitizingcompounds useful with the photoconductive compounds of the presentinvention can be selected from a wide variety of materials, for example,pyrylium dye salts, including thiapyrylium dye salts and selenapyryliumdye salts as disclosed in VanAllan et al U.S. Pat. No. 3,250,615;fluorenes, such as 7,12-dioxopractice to mix a suitable amount of thesensitizing compound with the coating composition so that, afterthorough mixing, the sensitizing compound is uniformly distributed inthe coated element. Other methods of incorporating the sensitizer or theeffects of the sensitizer may,-however, be employed consistent with thepractice of this invention. In preparing the photoconductive layers, nosensitizing compound is required to give photoconductivity in the layerswhich contain the photoconducting substances, therefore, no sensitizeris required in a particular photoconductive layer. However, sincerelatively minor amounts of sensitizing compound give substantialimprovement in speed in such layers, the sensitizer is preferred. Theamount of sensitizer that can be added to a photoconductorincorpor'atinglayer to give effective increases in speed can vary widely. The optimumconcentration in any given case will vary with the specificphotoconductor and sensitizing compound used. In general, increases inspeed can be obtained where an appropriate sensitizer is added in aconcentration range from about 0.0001 to about 30 percent by weightbased on the weight of the film-forming coating composition. Typically,a sensitizer is added to the coating composition in an amount by weightfrom about 0.005 to about 5.0 percent by weight of thetotal coatingcomposition.

Preferred binders for use in preparing the present photoconductivelayers are film-forming, hydrophobic v polymeric binders having fairlyhigh dielectric strength which are good electrically insulatingfilm-forming vehicles..Materials of this type include styrene-butadienecopolymers; silicone resins; styrene-alkyd resins; sili- 'cone-alkydresins; soly-alkyd resins; poly(vinyl chloride); poly(vinylidenechloride); vinylidene chlorideacrylonitrile copolymers; poly(vinylacetate); vinyl acetate-vinyl chloride copolymers; poly(vinyl acetals),such as poly(vinyl butyral); polyacrylic and meth- .acrylic esters, suchas poly(methyl methacrylate), po-

ly(n-butyl methacrylate), poly(isobutyl methacrylate), etc; polystyrene,nitrated polystyrene; polymethylstyrene; isobutylene polymers;polyesters, such as poly[etphenyl)terephthalate];'copolymers of vinylhaloarying resins of this type have been described in the prior art, forexample, styrene-alkyd resins can be prepared according to the methoddescribed in U.S. Pats. Nos. 2,361,019 and 2,258,423.

Suitable resins of the type contemplated for use in the photo-conductivelayers of the invention are sold under such trade-names as Vitel PE-lOl,Cymac, Piccopale 100, Saran F220, Lexan 105 and Lexan 145. Other typesof binders which can be used in the photoconductive layers of theinvention include such materials as paraffin, mineral waxes, etc.

Solvents useful for preparing coating compositions with thephotoconductors of the present invention can include a wide variety oforganic solvents for the components of the coating composition. Forexample, benzene; toluene; acetone; 2-butanone, chlorinated hydrocarbonssuch as methylene chloride; ethylene chloride; and the like; ethers,such as tetrahydrofuran and the like, or mixtures of such solvents canadvantageously be employed in the practice of this invention.

In preparing the coating compositions utilizing the photoconductingcompounds disclosed herein useful results are obtained where thephotoconductive substance is present in an amount equal to at leastabout 1 weight percent of the coating composition. The upper limit inthe amount of photoconductive material present can be widely varied inaccordance with usual practice. Typically, the photoconductive materialis present in an amount ranging from about 1 weight percent of thecoating composition to about 99 weight percent of the coatingcomposition. A preferred weight range for the photoconductive materialin the coating composition is from about weight percent to about 60weight percent.

Coating thicknesses of the photoconductive composition on a support canvary widely. A wet coating thickness in the range of about 0.001 inch toabout 0.01 inch is useful in the practice of the invention. A preferredrange of coating thickness is from about 0.002 inch to about 0.006 inchbefore drying although such thicknesses can vary widely depending on theparticular application desired for the electrophotographic element.

Suitable supporting materials for the photoconductive layers of thepresent invention can include any of the electrically conductingsupports, for example, various conducting papers; aluminum paperlaminates;

metal foils, such as aluminum foil, zinc foil, etc; metal plates, suchas aluminum, copper, zinc, brass, and galvanized plates; vapor depositedmetal layer such as silver, nickel or aluminum on conventional filmsupports such as cellulose acetate, poly(ethylene terephthalate),polystyrene and the like. An especially useful conducting supportmaterial such as poly(ethylene terephthalate) with a layer containing asemiconductor dispersed in a resin. A suitable conducting coatingcan beprepared from the sodium salt of a carboxyester lactone and the like.Such conducting layers and methods for their optimum preparation and useare disclosed in U.S. Pats. Nos. 3,007,901, 3,245,833 and 3,267,807.

The compositions of the present invention can be employed inphotoconductive elements useful in any of the well knownelectrophotographic processes which require photoconductive layers. Onesuch process is the xerographic process. In a process of this type, anelectrophotographic element held in the dark, is given a blanketelectrostatic charge by placing it under a'corona discharge to give auniform charge to the surface of the photoconductive layer. This chargeis retained by the layer owing to the substantial dark insulatingproperty of the layer, i.e., the low conductivity of the layer in thedark. The electrostatic charge formed on the surface of thephotoconductive layer is then selectively dissipated from the surface ofthe layer by imagewise exposure to light, thereby forming a latentelectrostatic image in the photoconductive layer.

The charge pattern produced by exposure is then developed or transferredto another surface and developed there, using any of the liquid or drydeveloper contiguous or spaced having layers of insulating material orother photoconductive material between layers or overcoated orinterposed between the photoconductive layer or sensitizing layer andthe conducting layer. It is also possibleto adjust the position of thesupport and the conducting layer by placing a photoconductor layer overa support and coating the exposed face of the support or the exposed orovercoated face of the photoconductor with a conducting layer.Configurations differing from those contained in the examples can beuseful or'even preferred for the same or different application for theelectrophotographic element.

The following examples are included for a further understanding of thisinvention.

EXAMPLE 1 Preparation of 2-(p-diphenylaminobenzylidene)-benzo[b]thiophen-3-one (Compound D) To an ethanol solution of 1.5 grams(0.01 mole) of benzo[b]thiophen-3 '2l-l-one and 2.7 grams (0.01 mole) ofp-diphenylaminobenzaldehydeare added 1.5 ml. of concentrated sulfuricacid. A deep red color appears. The solution is sitrred for 40 minuteswhile being maintained at an elevated temperature and therafter iscooled to room temperature. A yield of 4.2 grams of deep orange crystalsis obtained. Recrystallization from carbon tetrachloride andthen frompetroleum ether gives a product having a melting point range of 188-1 C.

Analysis C- H N S Calculated: 79.97 4.72 3. 5 7.9 Found: 79.8 5.0 3.57.8

EXAMPLE 2 Preparation of 2-(p-dimethylaminocinnamulidene)-benzo[b]thiophen-3-one (Compound E) The procedure of Example 1 isfollowed using an equimolar portion (1.75 grams) ofpdimethylaminocinnamaldehyde in place of the pdiphenylaminobenzaldehyde.The solution is refluxed with stirring for 35 minutes, to yield a tanprecipitate. The product is collected and purified by washing in turn inwater, dilute sodium hydroxide (10 percent), and finally water again toyield 2.0 grams of deep pur- 'tolylaminobenzaldehyde ple needles havinga melting point range of Analysis c H N Calculated: 74.24 5.57 4.5610.43 Found: 74.2 5.6 4.5 10.4

EXAMPLE 3 Preparation of 2-(p-di-p-tolylaminobenzylidene)-benzo[b]thiophen-3-one (Compound H) The procedure of Example 1 isfollowed using an equimolar portion (3 .0 grams) of di-pin place of thepdiphenylaminob'enzaldehyde. The resulting product is recrystallizedfrom ethyl acetate to give 3.5 grams of magenta crystals having amelting point range of from 193-l95C.

Analysis C l-l N S Calculated: 80.34 5.3 3.2 7.4 Found: 80.3 5.4 3.1 7.2

EXAMPLE 4 Analysis C H N S Calculated: 77.22 4.86 3.2! 7.36 Found: 77.!4.9 3.1 7.l

EXAMPLE 5 Preparation of 2-(4-diphenylamino-l-naphthyliden eybenzo[b]thiophen-3-one (Compound J) The procedure of Example 1 isfollowed using an equimolar portion (3.23 grams) of 4-diphenylamino-1-naphthy-aldehyde in place of the pdiphenylaminobenzaldehyde. Theresulting product is recyrstallized from ethyl acetate to give 3 .5grams of an orange solid having a melting point range of l84-187" C.

Analysis C H N 8 Calculated: 8!.73 4. 4 3.l 7.0 Found: 8L8 4.7 2.9- 7.1

The other compounds used in preparing the photoconductive compositionsand elements of the invention are prepared according to proceduresdescribed in-the literature. For example, Compounds A, B and F appear.in Zh. Obst. Khim. 3l (1), 17 (1961), while a compound similar toCompound C appears in Latvijas PSR Zinatu Akad. Vestis, Khim. Sci. (3),385(1963).

EXAMPLE 6 A composition in the form of a dope consisting of thefollowing materials is coated at a wet thickness of 150 microns on apoly(ethylene terephthalate)'film support bearing a conductive layercomprising vapor deposited nickel:

Photoconductor see below 0.25 g. Binderpoly(4,4'-isopropylidenebisphenyleneoxyethylene-coethylene terephthalate1.00 g.

Sensitizer 2,6-bis(4ethylphenyl)-4- (4-n-amyloxyphenyl)thiapyryliumperchlorate 0.0 Dichloromethane 9 .6

l g. 0 g.

The support is held on a coating block maintained at a temperature ofabout 32C during coating and until the solvent is removed. In a darkenedroom, the surface of the photoconductive layer so prepared is charged toa potential of about +600 volts under a corona charger.

, The layer is then covered with a transparent sheet bearing a patternofopaque and light-transmitting areas and exposed to the radiation from anincandescent lamp with an illumination intensity of about 75metercandles for 12 seconds. The resulting electrostatic charge patternis developed by cascading over the surface of the layer negativelycharged black thermoplastic toner particles on glass bead carriers. Thequality of the images reproduced using the various photoconductorsdescribed herein are set forth in the following table:

TABLE I Photoconductor none IO' H UO IP The elements containing thephotoconductors indicated in Table 11 below are then recharged under apositive corona source until the surface potential, as measured by anelectrometer probe, reaches about 600 volts. They are then exposed frombehind a stepped density gray scale to a 3000K tungsten source. Theexposurecauses reduction of the surface potentials of the elements undereach step of the gray scale from their initial potential, V,,, to somelower potential, V, whose exact value depends on the actual amount ofexposure received by the areas. The results of the measurements areplotted on a graph of surface potential V vs. log exposure for eachstep. The shoulder speed is the numerical expression of -104 multipliedby the reciprocal of the exposure in meter-candle-seconds required toreduce the 600 volt charged surface potential by volts. The elementshave speeds as thus measured as indicated in Table II.

TABLE II Speed Photoconductor B EXAMPLE 7 hour at room temperature. Thetwo solutions are then incorporated into a photoconductor-containingcoating solution to form a coating dope for each of the photoconductorslisted in Table III below. The photoconductor-containing solution isprepared according to the following composition:

Lexan 145 0.25 g. Photoconductor 025 g. Solution 1 4.50 gv Solution 27.70 g.

Each of the coating dopes thus produced is coated as in Example 6 toform photoconductive elements. Each element is then charged in turnpositively and negatively and exposed as in Example 6 through a steppeddensity gray scale. Speeds are obtained for both positive and negativecharging in the manner previously described, and are listed in TableIII.

When each of the elements listed in Table III is charged imagewise in amanner similar to that used in Example 6, except that the lightintensity is reduced by a power of 10, and developed in the same manner,a good reproduction is obtained in each case.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

I claim:

1. An electrophotographic element comprising a conductive supportbearing a layer of a photoconductive composition comprising an organicfilm-forming electrically insulating polymeric binder and an organicphotoconductor having the formula:

Y represents the group /CH=CH)R in which n is an integer from 0 to 2 andR is an aryl group. 2. An electrophotographic element according to claim1 wherein Z is a sulfur atom.

3. An electrophotographic element according to claim 2 wherein R throughR are each hydrogen atoms.

4. An electrophotographic element comprising an electrically conductivesupport bearing a photoconductive composition comprising an electricallyinsulating film-forming polymeric binder and an organic photoconductorhaving the formula:

whereini Y represents the group is an integer from 0 to 1; and R is sele cted from the group consisting of a phenyl radical, a methoxyphenylradical, a diphenylaminophenyl radical, a

dialkylaminophenyl radical, a phenylaminonaphthyl radical, and adiphenylamino-o-methoxyphenyl.

5. An electrophotographic element according to claim 4 wherein theorganic photoconductor is selected from the group consisting of2-(pdiphenylaminobenzylidene)-benzo-[b]thiophen-3-one,2-(p-di-p-tolylaminobenzylidene)-benzo[b]-thiophen- 3-one,2-(p-dimethylaminocinnamylidene)-benzo[b]- thiophen-3-one,2-(p-diphenylamino-omethoxybenzylidene)-benzo-[b]thiophen-3-one, 2-(4-'diphenylamino-l -naphthylidene )-benzo-[b]thiophen- 3 -one, 2-(p-phenylbenzylidene)-benzo[b]thiophen- 3 -one,2-(p-diethylaminobenzylidene)benzo[blthiophen-3 -one, and

2-(p-methoxybenzylidene)- benzo[b]thiophen-3-one. I

6. An electrophotographic element according to claim 4 wherein thephotoconductive composition is selected from the group consistingdiphenylaminobenzylidene)-benzo[b]-thiophen-3-one and2-(p-di-p-tolylaminobenzylidene)-benzo[b]- thiophen-3-one.

7. An electrophotographic element according to claim 1 wherein thephotoconductive composition comprises from about 0.005 percent to about5- percent by weight based on said photoconductive composition of asensitizer for said composition. 7

8. In an electrophotographic process wherein an electrostatic chargepattern is formed on an electrophotographic element, the improvementwherein said element is the element of claim 4. i

9. A 2-(p-diphenylaminobenzylidene)benzo[b]thiophen-3-one.

10. A 2-(p-dimethylaminocinnamylidene)benzo[b]- thiophen-3-one.

11. A 2-(p-diphenylamino-o-methoxybenzylidene)- benzo[b]thiophen-3-one.

12. A 2-(4-diphenylamino-l-naphthylidene)benzo[b]-thiophen-3-one.

13. A 2-(p-di-p-tolylaminobenzylidene)benzo[b]- thiophen-S-one.

2. An electrophotographic element according to claim 1 wherein Z is asulfur atom.
 3. An electrophotographic element according to claim 2wherein R1 through R4 are each hydrogen atoms.
 4. An electrophotographicelement comprising an electrically conductive support bearing aphotoconductive composition comprising an electrically insulatingfilm-forming polymeric binder and an organic photoconductor having theformula:
 5. An electrophotographic element according to claim 4 whereinthe organic photoconductor is selected from the group consisting of2-(p-diphenylaminobenzylidene)-benzo-(b)thiophen-3-one,2-(p-di-p-tolylaminobenzylidene)-benzo(b)-thiophen-3-one,2-(p-dimethylaminocinnamylidene)-benzo(b)-thiophen-3-one,2-(p-diphenylamino-o-methoxybenzylidene)-benzo-(b)thiophen-3-one,2-(4-diphenylamino-1-naphthylidene)-benzo-(b)thiophen-3-one,2-(p-phenylbenzylidene)-benzo(b)thiophen-3-one,2-(p-diethylaminobenzylidene)benzo(b)thiophen-3-one, and2-(p-methoxybenzylidene)-benzo(b)thiophen-3-one.
 6. Anelectrophotographic element according to claim 4 wherein thephotoconductive composition is selected from the group consisting of2-(p-diphenylaminobenzylidene)-benzo(b)-thiophen-3-one and2-(p-di-p-tolylaminobenzylidene)-benzo(b)-thiophen-3-one.
 7. Anelectrophotographic element according to claim 1 wherein thephotoconductive composition comprises from about 0.005 percent to about5 percent by weight based on said photoconductive composition of asensitizer for said composition.
 8. In an electrophotographic processwherein an electrostatic charge pattern is formed on anelectrophotographic element, the improvement wherein said element is theelement of claim
 4. 9. A2-(p-diphenylaminobenzylidene)benzo(b)thiophen-3-one.
 10. A2-(p-dimethylaminocinnamylidene)benzo(b)-thiophen-3-one.
 11. A2-(p-diphenylamino-o-methoxybenzylidene)-benzo(b)thiophen-3-one.
 12. A2-(4-diphenylamino-1-naphthylidene)benzo(b)-thiophen-3-one.
 13. A2-(p-di-p-tolylaminobenzylidene)benzo(b)-thiophen-3-one.